Remove "unused parameter" warnings on include of ruby.h

[flashcode]

This pull request removes "unused parameter" warnings when compiling with flag -Wunused-parameter (or with -Wall -Wextra).

The fix consists in fooling the compiler by adding a no-op instruction using the argument, like:

    (void)obj;

Steps to reproduce

1. Create a C source called test_ruby.c, with this content:

#include <ruby.h>

int main()
{
    return 0;
}

2. Compile the program with this command (using Ruby 3.1.0, but I'm pretty sure the problem is still there with latest versions):

gcc -Wunused-parameter -o test_ruby $(pkg-config --cflags ruby-3.1) $(pkg-config --libs ruby-3.1) test_ruby.c

Actual result

$ gcc -Wunused-parameter -o test_ruby $(pkg-config --cflags ruby-3.1) $(pkg-config --libs ruby-3.1) test_ruby.c 
In file included from /usr/include/ruby-3.1.0/ruby/internal/core/rstring.h:30,
                 from /usr/include/ruby-3.1.0/ruby/internal/arithmetic/char.h:29,
                 from /usr/include/ruby-3.1.0/ruby/internal/arithmetic.h:23,
                 from /usr/include/ruby-3.1.0/ruby/ruby.h:27,
                 from /usr/include/ruby-3.1.0/ruby.h:38,
                 from test_ruby.c:1:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_TAINTABLE’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:794:24: warning: unused parameter ‘obj’ [-Wunused-parameter]
  794 | RB_OBJ_TAINTABLE(VALUE obj)
      |                  ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_TAINTED_RAW’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:811:26: warning: unused parameter ‘obj’ [-Wunused-parameter]
  811 | RB_OBJ_TAINTED_RAW(VALUE obj)
      |                    ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_TAINTED’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:828:22: warning: unused parameter ‘obj’ [-Wunused-parameter]
  828 | RB_OBJ_TAINTED(VALUE obj)
      |                ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_TAINT_RAW’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:843:24: warning: unused parameter ‘obj’ [-Wunused-parameter]
  843 | RB_OBJ_TAINT_RAW(VALUE obj)
      |                  ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_TAINT’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:858:20: warning: unused parameter ‘obj’ [-Wunused-parameter]
  858 | RB_OBJ_TAINT(VALUE obj)
      |              ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_INFECT_RAW’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:874:25: warning: unused parameter ‘dst’ [-Wunused-parameter]
  874 | RB_OBJ_INFECT_RAW(VALUE dst, VALUE src)
      |                   ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:874:36: warning: unused parameter ‘src’ [-Wunused-parameter]
  874 | RB_OBJ_INFECT_RAW(VALUE dst, VALUE src)
      |                              ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h: In function ‘RB_OBJ_INFECT’:
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:890:21: warning: unused parameter ‘dst’ [-Wunused-parameter]
  890 | RB_OBJ_INFECT(VALUE dst, VALUE src)
      |               ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/fl_type.h:890:32: warning: unused parameter ‘src’ [-Wunused-parameter]
  890 | RB_OBJ_INFECT(VALUE dst, VALUE src)
      |                          ~~~~~~^~~
In file included from /usr/include/ruby-3.1.0/ruby/ruby.h:44:
/usr/include/ruby-3.1.0/ruby/internal/newobj.h: In function ‘rb_clone_setup’:
/usr/include/ruby-3.1.0/ruby/internal/newobj.h:173:22: warning: unused parameter ‘clone’ [-Wunused-parameter]
  173 | rb_clone_setup(VALUE clone, VALUE obj)
      |                ~~~~~~^~~~~
/usr/include/ruby-3.1.0/ruby/internal/newobj.h:173:35: warning: unused parameter ‘obj’ [-Wunused-parameter]
  173 | rb_clone_setup(VALUE clone, VALUE obj)
      |                             ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/newobj.h: In function ‘rb_dup_setup’:
/usr/include/ruby-3.1.0/ruby/internal/newobj.h:190:20: warning: unused parameter ‘dup’ [-Wunused-parameter]
  190 | rb_dup_setup(VALUE dup, VALUE obj)
      |              ~~~~~~^~~
/usr/include/ruby-3.1.0/ruby/internal/newobj.h:190:31: warning: unused parameter ‘obj’ [-Wunused-parameter]
  190 | rb_dup_setup(VALUE dup, VALUE obj)
      |                         ~~~~~~^~~

Expected result

No warnings at all.

Additional info

This was caused by commit 0300dec and affects versions 3.1.0 and above.

The fix has been tested with gcc and clang versions on Debian unstable:

$ gcc --version
gcc (Debian 12.2.0-13) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ clang --version
Debian clang version 14.0.6
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

The fix has NOT been tested with Ruby version > 3.1.0; other functions may be affected by the similar warning in newer releases (I did not fully check).

[shyouhei]

Good catch. As these functions remain for backward compatibility only, I have 0 motivation to actually use those parameters. This fix seems valid.

[jwillemsen]

Why not just remove the argument name, so for example make it

static inline bool
RB_OBJ_TAINTABLE(VALUE)
{
    return false;
}

[shyouhei]

@jwillemsen That's too new. We have to use the C language of '90s in this project.

[jwillemsen]

@jwillemsen That's too new. We have to use the C language of '90s in this project.

Ok, it has been fixed now, thanks!